A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, five major sections, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is positioned at the front, or “inlet” section of the engine, and includes a fan that induces air from the surrounding environment into the engine, and accelerates a fraction of this air toward the compressor section. The remaining fraction of air induced into the fan section is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section raises the pressure of the air it receives from the fan section to a relatively high level. In a multi-spool engine, the compressor section may include two or more compressors, such as, for example, a high pressure compressor and a low pressure compressor. The compressed air from the compressor section then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel into a plenum formed by combustor liners and a dome. The injected fuel is ignited in the combustor, which significantly increases the energy of the compressed air. The high-energy compressed air from the combustor section then flows into and through the turbine section, causing rotationally mounted turbine blades to rotate and generate energy. The air exiting the turbine section is exhausted from the engine via the exhaust section, and the energy remaining in the exhaust air aids the thrust generated by the air flowing through the bypass plenum.
The combustors in gas turbine engines typically operate at relatively high temperatures (e.g., >3500° F.). Such high temperatures can adversely impact the service life of a combustor. Thus, some form of cooling is typically provided for the combustor. One example of combustor cooling is known as effusion cooling. Effusion cooling involves providing a matrix of relatively small diameter effusion cooling holes through the combustor liners, and into which a flow of cooling air is admitted. The effusion cooling holes are typically angled relative to a surface of the combustor. This angle increases the length of the effusion holes through the liners, which increases the surface area from which the cooling flow removes heat from the liner, and generates a cooling film on the inner wall of the liners.
Although effusion cooling is generally effective, it does suffer certain drawbacks. For example, one characteristic of effusion cooling is that the film effectiveness may be relatively low at or near upstream sections of the combustor liner. Moreover, the cooling film, once it is sufficiently established, may be interrupted by one or more rows of major combustor orifices, such as dilution holes. As a result, some form of cooling augmentation may be used in the upstream sections of effusion cooled combustor liners and/or at locations downstream of major combustor orifices. Such cooling augmentation can complicate the construction of combustor and increase overall size, weight, and/or costs.
Hence, there is a need for an effusion cooling configuration that eliminates, or at least reduces the likelihood of, the above-noted drawbacks. Namely, there is a need for an effusion cooling configuration that does not exhibit a relatively low film effectiveness at or near upstream sections of the combustor, and/or a configuration in which the cooling film that is established is not interrupted by one or more rows of major combustor orifices, and/or that does not rely on one or more forms of cooling augmentation. The present invention addresses one or more of these needs.